Excluding those mentioned above and those defined in the patents mentioned immediately below the following Table, sealed beam lighting systems used in motor vehicles, and in particular those for providing forward illumination for automobiles, have generally not been designed with aerodynamic considerations in mind. As such, these lighting systems have exhibited poor aerodynamic performance. The typical minimum height of headlights (headlamps) found in such lighting systems is no less than about four inches (some as high as seven inches), including systems having four rectangular headlamps (two per side) as part thereof. Of equal importance is the total area of the headlighting system when viewed from the front. In many existing systems, total vertical areas of about seventy to ninety square inches are common. Understandably, such large areas contribute to poor aerodynamic performance of the respective motor vehicles. In this regard, the following Table is a list of many existing (again excluding those mentioned above and immediately below) multiple headlamp lighting systems illustrating the approximate height and total frontal (vertical) area of each system listed.
TABLE ______________________________________ Approximate Approx. Total System System Headlamp Height Area Sealed Beam Headlamps Type (Inches) (Sq. Inches) ______________________________________ 2 Lamp, Round 2D 7 77 4 Lamp, Round IC/2C 51/4 87 2 Lamp, Rectangular 2B 51/2 83 4 Lamp, Rectangular 1A/2A 4 96 2 Lamp, Rectangular 2E 4 48 ______________________________________
In a replaceable system not referred to in the above Table, a lamp capsule-holder component is replaced within a fixed reflector-lens combination (i.e., through a rear opening in the reflector) and sealed therein (i.e., using an O-ring seal). Examples of such systems are described in U.S. Pat. Nos. 4,623,958 (Van der Linde et al), 4,631,651 (Bergin et al), 4,569,005 (Bergin et al) and 4,569,006 (Bergin et al). These systems are especially designed to provide enhanced aerodynamics, and typically include only one headlight per side of the vehicle. The lens, usually of impact-resistant plastic, is shaped to match the vehicle's front contour and is usually fixedly secured relative thereto. The replaceable capsule-holder component (both members being sealed together to define an integral, replaceable component) is then rotatively or directly inserted within the assembly's reflector, which may or may not include the lens as part thereof. Typically, the lens is a separate component and is also hermetically sealed to the reflector.
Although such a system provides desired aerodynamic features, alignment between the capsule and holder (and thus with the reflector in which this integral component is positioned) is critical and sometimes difficult to attain. That is, there exists a potential problem regarding close tolerance control, particularly between capsule and holder members during assembly thereof. Attainment of such close tolerance control is usually accomplished through utilization of relatively complicated procedures using complex equipment. With lighting systems such as those of the aforementioned replaceable type and those mentioned in the Table above, there is also the problem that when a headlamp burns out, a major portion of the forward light pattern is lost due to the inability of only the single headlamp remaining (assuming a two headlamp arrangement is utilized) to provide sufficient forward illumination. In a four headlamp system (two per side) a significant reduction in output on one side of the vehicle occurs. Still another problem in a system with separate headlamps being used for high and low beam is the inherent lack of flexibility, particularly in optimizing both high and low beam patterns. In those systems in which two filaments are employed in a single lens-reflector combination, the lens element can typically be optimized for only one pattern. Switching to the second filament results in a compromised light distribution.
Lastly, and perhaps most significantly, headlamp systems of the replaceable type and of the type described in the above Table typically mandate relatively complex alignment procedures (which are usually only capable of being accomplished by a skilled technician) to both maintain the headlamp in required alignment and to assure that a replacement therefor is in turn also correctly oriented within the vehicle. Understandably, such requirements add to the cost of maintaining the headlamp system using such components and thus of the vehicle utilizing same.